FIG. 1 is a sectional illustration of a conventional nuclear reactor fuel assembly 10 typically used in commercial light water nuclear reactors for electricity generation throughout the world. Several fuel assemblies 10 are shipped to and placed in a reactor in close proximity to sustain a nuclear chain reaction. A fluid moderator and/or coolant conventionally passes through fuel assembly 10 in an axial direction, enhancing the chain reaction and/or transporting heat away from the assembly 10.
As shown in FIG. 1, fuel assembly 10 includes multiple fuel rods 14 containing fissile material and extending in the axial direction within the assembly 10. Fuel rods 14 are bounded by a channel 12 that forms an exterior of the assembly 10, maintaining fluid flow within assembly 10 throughout the axial length of assembly 10. Conventional fuel assembly 10 also includes one or more conventional fuel spacers 18 at various axial positions. Fuel spacer 18 permits fuel rods 14 to pass through grid-like openings in spacer 18, thereby aligning and spacing fuel rods 14. One or more water rods 16 or other assembly features may also pass through spacer 18, and grid size and shape, and the overall shape of spacer 18 may vary across different designs of assembly 10.
FIG. 2 is an illustration of a related art fuel spacer 18 from an axial direction. As shown in FIG. 2, conventional spacer 18 includes several grid openings 41, which may be formed by several unioned internal spans 42. Perimeter band 49 may enclose spacer 18 and include one or more bathtubs 44 that contact channel 12 (FIG. 1). As shown in FIG. 2, several fuel rods 14 may pass through spacer 18 through corresponding grid openings 41, when used in an assembly. Grid openings 41 may be of a substantially similar size and positioned in rectilinear fashion as shown in FIG. 2, or may be positioned and sized differently to accommodate other fuel designs. For example, grid openings 41 for water rods 16 may be larger than grid openings 41 for smaller fuel rods 14. Alternatively, all grid openings 41 may be a same size, and one or more rod contacts 46 may be used to bring fuel rods 14 into rigid contact with spacer 18 if grid openings 41 are larger than a diameter of fuel rod 14. For example, rod contacts 46 may be attached to one or more sidewalls 45 of grid opening 41 and extend inward to contact fuel rod 14 and rigidly connect fuel rod 14 to spacer 18 in a transverse direction.